Water Resources Collections and Archives

In  California’s  Central  Valley,  dams  block  95  percent  of  historic  salmonid  habitat.    To  restore access by spring-run chinook salmon (Onocorhynchus tshawytscha) and other anadromous fish to approximately 12 miles of upstream spawning habitat on Clear Creek (drainage areas 720 km 2 ), the  US  Bureau  of  Reclamation  removed  the  McCormick-Saeltzer  Dam  in  November  2000.Previous  studies—the  most  recent  in  2004—identified  significant  sediment  mobilization  since dam removal at, and above, the former dam site.  In October 2011, we resurveyed two previously established  cross  sections at 26  m and 103.3  m upstream  of  the  dam  site  and  conducted  a  long profile  of  the  thalweg  from  the  dam  site  to  175  m  upstream.   We  also  replicated  previous  site photographs,  drew  vegetation  maps  and  compared  2010  aerial  photographs  to  those  from  1998 and  2004  to  assess  vegetation  change  and  erosion  patterns.   Our  results  documented  little incremental  erosion  at  and  upstream  of  the  dam  site  since  2004,  suggesting  that  sediment mobilization post-dam removal has largely stopped.  Establishment of riparian vegetation may be stabilizing remaining sediment deposits.